hesitation can be caused by a vac leak.

 

yeah i think i have one too, i hear air sucking and so i'll spray carb cleaner and / or starting fluid around that area, but there wasn't any engine rpm increase, so I wrote it off as the air intake.

 

an easy way to test for vac leaks in the accy stuff is to simply cap off the numerous vac ports at the intake. caution - you lose power brakes.

i never had much luck with spraying stuff. the fan blows it away too fast. also, carb cleaner, etc, is no longer flammable like it used to be.

 

Could it possibly be the Plenum gasket? or a cloged air filter?

 

plenum - maybe, probably not. a bad hesitation caused by a vac leak is generally a really bad vac leak. the plenum leak is generally very small and subtle.

clogged air filter - i doubt it. this would cause the engine to starve for air and not recover.

a vacuum gauge is real cheap at the part store. it can give you a little indication of that things are ok or not. but the best test is to cap off the manifold's accy ports and do a test rev or a short test drive. also, if its 4wd, the cad lines are a common place to leak.